Thank you for the additional information.
To answer the question you asked, yes, your client can sue you because anyone can sue anyone. However, the real issue would be whether there is a valid basis upon which to sue.
If there is a party alleging that their image was stolen or used without their permission, they have the legal right to sue any party using the image for infringement of their intellectual property rights. It would be incumbent upon them to prove that they have the legal right to the image and that you are infringing upon their copyright. With respect to your client suing you, whether or not they have a valid legal basis upon which to sue would depend on the cause of action
. Because it's been a number of years, the statute of limitations may have passed for some of their claims, i.e. contract claims. If, however, the cause of action were to arise from their being sued, then there would likely not be a statute of limitations problem.
Essentially, it all comes down to what the party alleging infringement can prove, what you can prove with respect to the image (i.e. proof that you did not steal it), and what your contract with the client specified with respect to rights and obligations.
Please let me know if this has answered your question or whether you need additional information. Thank you.